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The Centers for Disease Control and Prevention has tabulated estimates of the toll the 2009 H1N1 pandemic took in the United States. The numbers are sobering and require no additional comments. The CDC tabulated the numbers through direct observation in 62 counties covering 13 metropolitan areas of 10 states, which were then extrapolated to the entire US Population. So without further ado, here is what the 2009 H1N1 pandemic did in the US.

Total Cases – 60,837,748 (yep, millions) which break down as such:

0-17 years – 19,501,004

18-64 years – 35,392,931

65+ years – 5,943,813

Hospitalizations – 274, 304 which break down as such:

0-17 years – 86,813

18-64 years – 160,229

65+ years – 27,263

Deaths – 12, 469 which break down as such:

0-17 years – 1,282

18-64 years – 9,565

65+ years – 1,621

So, to put this in perspective. If you’re a 30-year-old such as myself, over 9,500 of our peers have died; 1,282 of our children are dead, and 1,621 of our parents are gone, all due solely to H1N1 flu. Chances are then, there is someone out there who lost his spouse, child and one parent to this disease. Makes you think twice about not vaccinating no?

Influenza, or “the flu” is an extremely contagious respiratory illness caused by influenza A or B viruses. Flu appears most frequently in winter and early spring. The flu virus attacks the body by spreading through the upper and/or lower respiratory tract. There are 3 types of flu viruses, A, B and C which can cause the flu, and new strains (especially the A type) evolve every few years.

Type A viruses are responsible for major flu epidemics every few years. Type B is less common and generally results in milder cases of flu. However, major flu epidemics can occur with type B every three to five years. There is a third type of virus, C, which also can infect but does not produce flu symptoms.

What are the symptoms/effects of the flu?

Besides generally making one feel miserable, here is a list of some of the most typical flu symptoms/effects.

Headaches

Severe aches and pains in the joints and muscles and around the eyes

Cough

Respiratory congestion

Fever

Chills

Fatigue & exhaustion

Severe flu can lead to pneumonia

Sore throat and watery discharge from your nose

Are there any complications that can arise from the flu?

The most common flu complications include viral or bacterial pneumonia, muscle inflammation, and infections of the central nervous system or the sac around the heart. Other flu complications may include ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.

Those at highest risk for flu complications include adults over 50, children ages 6 months to 4 years, nursing home residents, adults and children with heart or lung disease, people with compromised immune systems (including people with HIV/AIDS), and pregnant women.

How does flu spread?

The flu is spread from person to person through respiratory secretions and typically sweeps through large groups of people who spend time in close contact, such as in daycare facilities, school classrooms, college dormitories, military barracks, offices, and nursing homes.

Flu is spread when a person inhales droplets in the air that contain the flu virus, make direct contact with respiratory secretions through sharing drinks or utensils, or handle items contaminated by an infected person. In the latter case, the flu virus on your skin infects you when you touch or rub your eyes, nose, or mouth. That’s why frequent and thorough hand washing is a key way to limit the spread of influenza. Flu symptoms start to develop from one to four days after infection with the virus.

Will one catch the flu if one goes out in the cold or gets wet by cold rain?

No. The flu is a viral infection; you need to come in contact with the flu virus to get infected. Feeling cold or being wet does not give you the flu. It might give you a runny nose though and other symptoms that may be reminiscent of the flu, but it does not cause a flu infection.

What are the symptoms/effects of the flu vaccine?

The most common side effects of the flu vaccine (both inactivated and LAIV) include mild:

Swelling at the site of the injection (inactivated only)

Headache

Cough

Body ache

Fever

When should one get the flu vaccine?

As soon as it is available.

How many types of flu vaccines are there?

There are two types of flu vaccine. Inactivated and LAIV. The inactivated vaccine is given as a shot, generally in the arm, while the LAIV version is a nasal spray. The main difference between the two is that the inactivated, or the shot, contains dead viruses, whereas the LAIV version contains alive, but extremely weakened, viruses. Because of that, the spray is expected to be more effective in inducing an immune reaction than the shot.

Why is the flu vaccine different every year?

Two of the three flu viruses are responsible for causing flu, type A and type B. Type A has 16 subtypes, while Type B is not categorized by subtypes. They both can mutate, especially type A which results in new strains every few years. Every given year, any combination of various strains of the various subtypes of A and of Type B can be in circulation and causing flu.

Every given year, both the LAIV and Inactivated vaccine contain three strains of influenza virus that are chosen each year based on what scientists predict will be the circulating viruses for the flu season. Given the long production times, it is impossible to know for sure which strains will be prevalent in the upcoming season, so every year scientists have to do their best to predict what they think will be the prevalent strains. Usually this process is done months ahead of the actual flu season. This is why the flu vaccine is different each year, and why we have to get re-vaccinated each year.

Which strains does the 2010 vaccine protect against?

Every year, the flu vaccine, protects against 3 specific strains of viruses that cause flu. The 2010 vaccine protects against two A viruses and one B virus. This year the vaccine protects against these 3 strains:

an A/California/7/2009 (H1N1)–like virus (Swine Flu)

an A/Perth/16/2009 (H3N2)–like virus

and a B/Brisbane/60/2008–like virus

Can you get the flu from the flu vaccine?

No! You cannot get the flu from the flu vaccine. You may, however, experience some flu-like symptoms, which can be experienced from any vaccine in some cases and doesn’t have anything to do with the actual disease you’re being inoculated against.

How effective is the flu vaccine?

The effectiveness of the flu vaccine depends on the strains in circulation and the strains the vaccine prevents from. When the vaccine viruses and circulating viruses are well-matched, the vaccine can reduce the chances of getting the flu by 70% to 90% in healthy adults.

Can you get the flu, even if you get vaccinated?

Yes. Firstly, as we already saw, the 3 strains in the flu vaccine have to be guessed in advance of the flu season. If there is a good match between the predicted strains and the actual strains in circulation, the vaccine will provide good protection. On the other hand, even if there is a perfect match, no vaccine is 100% effective, so even then a person who got vaccinated may still develop the flu. However, in general, people who are vaccinated experience milder symptoms than the non-vaccinated ones.

Who should get the flu vaccine?

Except for high risk groups that are advised to skip the vaccine, it is recommended that everyone over 6 months of age should get the flu vaccine.

Who should not get the flu vaccine?

Anyone with a severe allergy to eggs or egg products should not get a flu shot. Other people who should not get a flu shot include:

Infants under 6 months old.

Anyone who has had a severe reaction to a past flu shot or nasal spray.

Someone with Guillain-Barre syndrome.

People with moderate to severe illness with a fever; they should be vaccinated after they have recovered.

How Long Am I Contagious After I Get the Flu?

You are contagious for up to seven days after the onset of the flu, although the flu virus can be detected in secretions up to 24 hours before the onset of symptoms. This means you might transmit the flu virus a full day before your flu symptoms begin.

In young children, the flu virus can still be spread in the secretions even into the second week of illness.

How Can I Prevent the Flu?

To prevent the flu, be sure to keep your hands clean — making sure to wash them frequently to remove germs — and get a flu shot. The CDC develops a flu vaccine based on the type A strain that they believe will be most prevalent in the coming flu season. This is the vaccine you get with the annual flu shot or FluMist nasal spray.

Give me some statistics please?

-Every year during flu season, 1 in 20 Americans will contract the disease. Some years incidence can be as high as 1/5.

Today we will look at the recent recommendation by the CDC, the American College of Obstetricians and Gynecologists, that, all people over 6 months of age, including pregnant women receive the flu vaccine. Anti-vaccination groups have already come out, insinuating that the safety of the flu vaccine given during a woman’s pregnancy has not been established. Is that true? Are there any studies that have looked at the safety of the influenza vaccine for pregnant women? The answer is yes, at the very least there is one that I was able to find, using simply Google.

Study Summary – The objective of the study was to “evaluate the safety of influenza vaccine that is administered in the second or third trimester of gestation”. A retrospective electronic database search of 5 influenza seasons (July 1, 1998, to June 30, 2003) was performed at a large multispecialty clinic in Houston, Texas. Immunization rates were calculated, and outcomes of pregnancy were compared between healthy women who received influenza vaccine, and a control group of healthy unvaccinated women who were matched by age, month of delivery, and type of medical insurance.

Results – Among 7183 eligible mother-infant pairs, only 252 pregnant women (3.5%) received the influenza vaccine. The mean gestational age at the time of influenza vaccination was 26.1 weeks (range, 14-39 weeks). No serious adverse events occurred within 42 days of vaccination, and there was no difference between the groups in the outcomes of pregnancy (including cesarean delivery and premature delivery) and infant medical conditions from birth to 6 months of age.

Conclusion – This study provides good evidence that pregnant women who receive the flu vaccine during the last 2 trimesters of the pregnancy, and their babies at least up to 6 months of age, face no more risks or complications than pregnant women who do not receive the flu shot during the last 2 trimesters of their pregnancy, and their babies up to 6 months of age. It appears the claims of the anti-vaccination crowd are rejected, at least as far as this study is concerned. The authors concluded as such:

Influenza vaccine that was administered in the second or third trimester of gestation was safe in this study population.

Study Summary – The objective of this study was to assess the effect of seasonal influenza vaccination during pregnancy on laboratory-confirmed flu infections in infants up to 6 months of age. A total of 1160 mother-infant pairs were included in the study. The women gave birth during the regular flu season. Some of them received the flu vaccine, some didn’t. The assignment to either receive the flu vaccine or not was not random. The study authors looked at actual lab-confirmed influenza illnesses (ILI), and ILI hospitalization rates of the infants as the main outcomes. They compared ILI confirmed rates, and ILI hospitalization rates between the infants born to vaccinated mother and infants born to unvaccinated mothers.

Results – Infants born to vaccinated mothers were less likely than infants born to unvaccinated mothers to contract ILI. Specifically:

Significantly higher hemagglutinin inhibition antibody levels at birth and at 2 to 3 months of age

Conclusion – Methodologically, the main design issue is that test subjects were not assigned randomly to either the vaccine or no-vaccine. Furthermore, it appears from the abstract at least, that the mothers in the no-vaccine group did nor receive a placebo shot. The implication is that they simply did not receive a shot and were aware of it, which would affect the blinding as well.

When taken together these two facts should lower our reliance on the results, although not negate it entirely. The differences of 41% and 39% are too big to be due simply to bias introduced by these design issues. So the conclusion should be that given the large sample size and the large differences between the two groups, this study is highly indicative that babies born to vaccinated mothers do receive a tangible benefit from the vaccine, but the actual reduction in infection and hospitalization rates may be a little less than the numbers reported in this study. These conclusions should be compared to other studies, hopefully studies that had better blinding and randomization.

The author’s own conclusion is as such;

Maternal influenza vaccination was significantly associated with reduced risk of influenza virus infection and hospitalization for an ILI up to 6 months of age and increased influenza antibody titers in infants through 2 to 3 months of age.

Health-care associated influenza outbreaks are a common and serious public health problem that contribute significantly to patient morbidity and mortality and create a financial burden on health care systems. In a new policy statement, the American Academy of Pediatrics (AAP) recommends that all health care personnel should be required to receive an annual influenza vaccine. The policy, “Recommendation for Mandatory Influenza Immunization of All Health Care Personnel,” published in the October 2010 print issue of Pediatrics (published online Sept. 13), states that “despite the efforts of many organizations to improve influenza immunization rates with the use of voluntary campaigns, influenza coverage among health care personnel remains unacceptably low.” Annual influenza epidemics account for 610 660 life-years lost, 3.1 million days of hospitalization, and 31.4 million outpatient visits. Flu generates a cost burden of approximately $87 billion per year in the United States. Mandatory influenza immunization for all health care personnel is “ethically justified, necessary and long overdue to ensure patient safety,” according to the statement. The influenza vaccine is safe, effective, and cost-effective, so health care organizations must work to assuage common fears and misconceptions about the influenza virus and the vaccine.